This invention relates generally to pulsation reducers and more particularly to pulsation reducers for use in applications such as positive displacement fluid pumps and is intended to reduce impact loading on valves, fluid conduit pump bearings, pump drives, piston seals, on piston type pumps, and gear teeth and seals and housings of gear pumps etc.
Small high pressure positive displacement pumps particularly of the type that are often used in spray wash machines for example that disclosed in U.S. Pat. No. 3,238,890 Sadler et al issued Mar. 8, 1966 are often driven directly by an 1800 rpm electric motor, and utilize two opposed pistons, thus 3600 cycles per minute of pressure impulses and flow variations must be accomodated. If no pulsation reducer is used the whole pressure system is subject to impact loading (water hammer) at that frequency so that a pump delivering an average pressure of five hundred p.s.i. can, depending on the resiliency of the piping, hose etc., be subject to very great pressure variations a condition which is very damaging to pumps and flexible hose etc.
In U.S. Pat. No. 3,867,963, several embodiments of pulsation reducers utilizing a flexible wall structure consisting essentially of a Belleville spring-cover plate assembly having on its convex side a covering elastomeric diaphragm, sealingly held in a recess by its outer periphery so that on being subjected to fluid pressure the flexible wall structure will deflect outwardly to a mean position, and thereafter oscillate inwardly and outwardly responsive to pressure variations.
The original application also disclosed restrictors to inhibit outward flow of fluid from the pulsation reducer, and disclosed an over pressure control valve wherein deflection of a flexible wall structure byond a predetermined limit lifted a valve plunger from the seat of the control valve to permit return of over pressure fluid back to the intake side of the pump.
While I did state in original application "a pressure limitation valve . . . actuated by an adjustable lost motion linkage . . . may be incorporated into the body of my pulsation reducer, to permit return of over pressure fluid", I did not adequately illustrate how a pressure limitation valve could be arranged to function as an unloading valve, i.e. when pressure builds up in the system byond a predetermined working pressure a valve plunger is lifted from the seat of the pressure limitation valve, where it is normally held by internal pressure, and is moved away from the seat by a spring thereby permitting fluid to flow to the intake side of the pump through the unloading valve, and permit the pressure in the system to drop to a predetermined lesser pressure than the working pressure without re-engaging the valve plunger. When the pressure in the system is permitted to drop still lower, the flexible wall structures moves inwardly still further and force the valve plunger onto its seat to stop the flow of fluid to the intake side of the pump, so that internal pressure within the system will again rise to the working pressure.
By adjustably mounting the seat portion of the pressure limitation valve on one flexible wall structure, and the valve plunger actuating portion of the pressure limitation valve on the opposed flexible wall structure, the relative motion between the valve parts is doubled relative to using the movement of only one flexible wall for this purpose. This makes valve actuation less sensitive to small movements of the flexible wall structure and makes `in operation` adjustments of upper and lower pressure limits possible. Furthermore, in the event of failure of either flexible wall structure because of, for example, the breaking of a Belleville spring, pressure in the system will immediately be reduced to a pressure less than the working pressure of the system.